DESCRIPTION: (Investigator's Abstract) The nasal cavity of most mammals contains several chemoreceptor systems and putative chemorecptor systems - three of which, the vomeronasal organ (VNO), the nervus terminalis (NT) and olfactory system are thought to be involved in chemical communication between individuals (pheromone communication). Communication by chemical signals in humans is often dismissed on introspective evidence but subliminal effects may occur, as in menstrual synchrony in women who live together. The vomeronasal organ is absent in human adults but its CNS target, the corticomedial amygdala, is present and appears to be involved in emotional, social and sexual function - as it is in mammals that retain the VNO. The nervus terminalis is also present in humans, constituting the only cranial nerve of unknown function. Basic information on the original function of these systems which evolved in earlier vertebrates may help to elucidate their present function in humans - in addition to the knowledge gained on basic neurobiological processes. Experiments proposed here include 1) a study of the mechanisms of chemical sensitivity in primary VN receptor neurons which will provide data on chemosensory transduction in an olfactory-type neuron lacking cilia, 2) investigation of the influences of VN and NT input to the central nervous system, especially their ability to release luteinizing hormone releasing hormone (LHRH) in the brain and thereby influence reproductive behavior, 3) studies of the effect of prepubertal VNO removal on adult sexual behavior - investigating the extent to which learning of maternal chemical signals is involved. The hamster serves as a model system for these studies. The nervus terminalis is a system, some of whose neurons contain LHRH, that connects the nose with other LHRH-containing neurons in the brain. In addition, to the experiments on nervus terminalis function in adult mammals, the investigator will also 4) test the hypothesis that all LHRH neurons of the vertebrate forebrain originate in the developing nose and migrate to the brain along the nervus terminalis.